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I secure the rifle in the best way available to me, when/wherever I am when the sight needs to get moved - whether @ home when changing sights, or @ the range while zeroing.
@home I clamp the receiver in vise w/padded jaws.
@range I have a strong companion hold the rifle as solidly as possible, but if alone I lay it with the side "down" that I want to move the sight towards.
Before moving a sight for a windage adjustment, however, I always lay a small piece of yellow masking tape across the barrel just ahead or behind the sight & make a pencil mark at some convenient point that abuts a corner of the sight.
Now, when the sight's moved for an adjustment, you will be able to see how much the sight's actually moved, ILO guessing.
A rear sight is moved in the direction you wish to move the boolit impact: a front sight is moved in the opposite direction the boolit impact is to be moved.
If the sight's to be completely removed, they're usually driven out towards the RH side of the rifle (looking at the sight as if shooting).
The sights are re-installed in the opposite direction.
Use a non-marring punch/drift to avoid damaging the sight - I use the pivot pin from a common househole interior dood hinge.
Don't "tap" it - use a heavy-enough hammer (12 to 16oz) and smack the drift like it owes you money.
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